12 Facts About Belly Buttons

Belly buttons are many things bundled up into one tiny knot: Collectors of lint. Harborers of bacteria. Objects of desire. Symbols of creation and birth. From the gross to the sexy to the spiritual, there’s a lot to unpack about the belly button’s place in history, culture, science, and religion. Let's get started.

1. THEY'RE REALLY JUST SCARS.

That little spot in the center of your belly marks the place where your umbilical cord once connected you to your mom’s placenta. When that cord is cut, a little, shriveled piece of it gets left behind. It eventually falls off—usually within the first week of a baby’s life—and what remains is a scar. Of course, “belly button” sounds a lot cuter than “belly scar.”

2. DOCTORS CAN’T CHOOSE A BABY'S BELLY BUTTON SHAPE …

Whether your belly button caves in or sticks out has nothing to do with how your doctor cut or clamped your umbilical cord. It all comes down to the amount of space between the skin and the abdominal wall, which determines how much skin—and scar tissue—is left behind. "You can't do anything to make sure babies have an innie or outie," Dr. Dan Polk, a neonatologist at Children's Memorial Hospital in Chicago, told the Chicago Tribune. "It has to do with how much baby skin leads onto the umbilical cord from the baby's body. Less skin makes an innie; more skin makes an outie." About 90 percent of people have innies, and the rest are outies. In some cases, an outie orientation is the result of an umbilical hernia, which occurs when part of the intestine pokes through the umbilical opening in the abdominal wall. It usually seals up naturally by the time a child reaches the age of 2, but more persistent cases may require surgery.

3. … BUT A COSMETIC SURGEON CAN TURN AN OUTIE INTO AN INNIE.

For those who don't like their outie, cosmetic surgery is an option—albeit a drastic one. Umbilicoplasty is a surgery that alters the size or shape of the belly button, often by removing excess skin or tightening abdominal skin. A 1971 article in the Honolulu Star-Bulletin called belly button beautification the “newest gimmick in the cosmetic surgery game.” The article cited a Japanese physician who had performed more than 3000 navel operations in the ‘60s and early ‘70s for about $80 to $150 a pop. (Now, the surgery costs about $2000 in the U.S.)

An article in The Ottawa Citizen suggested that the surgical technique dates back to the early 1900s, when it was usually done as a corrective measure in conjunction with tummy tuck surgeries, which often displace the belly button. Even if there’s no medical need, a patient can now opt for umbilicoplasty to get the “ideal” shape. “What was favored through the Greek, Roman, and Western civilization to our time is an oval belly button that is more or less vertically oriented,” New York City cosmetic surgeon Bruce Nadler told the paper in 2002, when these surgeries were starting to become more popular. By contrast, Nadler said, horizontal belly buttons are considered more desirable in Asian cultures because they’re associated with good fortune.

4. MOST MAMMALS HAVE ONE.

Dogs, chimpanzees, lions, and armadillos have one, but their navels aren’t always easy to spot. For one, most mammalian mothers chew off the umbilical cord attached to their newborns, leaving a flat scar that’s harder to detect than a human belly button. Gorillas and chimpanzees are an interesting case for navel-gazers because they have what some scientists call an “in-betweeny”—a navel that looks like a human’s but is neither an innie nor an outie.

However, there are a few notable exceptions to the mammal belly button rule. Platypuses, which lay eggs, have no umbilical cord and therefore no belly button. As for marsupials like kangaroos and koalas, their umbilical cords generally fall off while they’re still inside mom's pouch, so a scar never forms.

5. THE FEAR OF BELLY BUTTONS IS CALLED OMPHALOPHOBIA.

Some people feel anxious, afraid, or disgusted when their belly button is touched or when someone else's bare midriff is on display. This is called omphalophobia, which stems from the Greek word omphalo for navel. This fear is believed to be linked to the navel's association with umbilical cords and wombs, or perhaps the irrational childhood fear that a belly button will come undone, letting one’s guts spill out. The phobia has gained more national exposure ever since TV personality Khloé Kardashian admitted she has a fear of belly buttons.

6. IF YOU POKE IT, YOU MIGHT SUDDENLY GET THE URGE TO PEE.

Speaking of touching your belly button (and all the grossness that comes with it), you may feel a tingly sensation when you stick your finger in it. That’s because you're stimulating fibers lining the inside of your abdomen, which then send a message to your spinal cord. As Dr. Christopher Hollingsworth of NYC Surgical Associates explained to BuzzFeed, “Because your spinal cord at that level is also relaying signals from your bladder and urethra, it feels almost the same. You interpret this as discomfort in your bladder."

7. THEY CAN LEAK URINE.

In a similar vein, a rare abnormality can cause urine to leak out of the belly button. In the early stages of pregnancy, a tube called the urachus connects a fetus’s bladder and belly button and allows urine to drain. It usually atrophies and turns into a scar on the bladder at birth or soon after, but not always. Some people may never know they still have all or part of their urachus attached because it only becomes a problem if the tube doesn’t close up. In those cases, urine can travel up through the urachus and leak out of the umbilicus (navel). Surgery is generally needed to fix this issue.

8. THEY GROW SPECIAL FLUFF-CATCHING HAIRS.

Have you ever wondered why bits of lint keep collecting in your belly button, despite your best efforts to keep clean? Blame it on a special type of hair that grows in navels. These hairs have tiny barbs that protrude and rub against your clothing, causing small fibers to scrape off. The hairs are arranged in concentric circles, which act as a funnel and suck fluff into your navel. Those who shave their stomachs or don't grow a lot of body hair to begin with likely don't have many problems with lint.

9. THEY CONTAIN THOUSANDS OF KINDS OF BACTERIA.

Beyond lint, a lot of dead skin, discarded fat molecules, and thousands of bacteria also live in your navel. One 2012 study led by the aptly named Belly Button Biodiversity project documented 2368 types of bacteria in the navels of 66 study participants. Fret not, though: They help to protect you against harmful pathogens. “We know that without these microbes our immune systems won’t function properly,” the head of the project, Dr. Rob Dunn, said in a statement. “In fact, this collection of microbes must have a certain composition—must form a certain microbial ecosystem—in order for our immune system to function properly."

10. THEY USED TO BE BANNED ON TV.

In Western culture, belly buttons have been regarded as "a feminine sexual center since ancient times," according to the Online Etymology Dictionary. As such, they were deemed too lewd to show on television, according to the Code of Practices for Television Broadcasters, established by the National Association of Broadcasters in 1951. Barbara Eden, who played the titular role in I Dream of Jeannie, said network executives at NBC held meetings over whether to let her flash her navel during the show’s run in the ‘60s. Her producer, George Schlatter, “said he had never seen so many suits sitting around a table in his life discussing someone's anatomy,” Eden told the TODAY show. Although Eden’s genie get-up never ended up revealing her belly button, other shows started to push the envelope around the same time. The belly-button ban technically remained in effect until 1983, but it wasn’t exactly enforced. Yvette Mimieux of Dr. Kildare became the first actress to bare her navel on television in 1964, and others followed suit soon after.

11. THEY ARE THE SOURCE OF A LONGSTANDING THEOLOGICAL DEBATE.

Among Christians, the debate over whether Adam and Eve had belly buttons is a little like the age-old “chicken or egg” question. One popular argument holds that Adam and Eve weren’t born naturally from a mother, and thus they wouldn’t have had umbilical cords or belly buttons. Others disagree for various reasons and insist that navels have been around since the dawn of time. Both Raphael and Michelangelo depicted Adam and Eve with navels in their artwork (including the Sistine Chapel's ceiling painting), leading one 17th-century doctor and philosopher to decry these “vulgar errors,” according to the bookUmbilicus and Umbilical Cord by Mohamed Fahmy. Other artists tried to avoid the issue altogether by concealing the couple’s abdomens with foliage, forearms, or long hair.

A few centuries later, a U.S. House of Representatives subcommittee refused to distribute a booklet called Races of Man to World War II soldiers because it contained pictures of Adam and Eve with navels. Members of the committee ruled that this image “would be misleading to gullible American soldiers.”

12. THEY ARE CELEBRATED IN SOME CULTURES.

Think of Middle Eastern belly dancing and midriff-baring Indian attire. In some places around the world, the navel holds cultural and even spiritual significance. Some Hindus believe that a lotus emerged from the god Vishnu’s navel, and at the center of the flower was Brahma—the creator of the universe. Likewise, in Japan, the belly button may represent the point where life begins. In the Middle Jōmon period (2500-1500 BCE), Japanese artists emphasized the appearance of navels on their human-like figurines. Today, a belly button festival is held annually in the town of Shibukawa in central Japan. “The belly button is traditionally believed to be located in the middle of the body and the most important part,” festival organizer Kazuo Yamada told Reuters. “Our town, Shibukawa, is also called the belly button of Japan, and that is how this festival began.”

9 Fascinating Facts About the Vagus Nerve

The vagus nerve is so named because it “wanders” like a vagabond, sending out sensory fibers from your brainstem to your visceral organs. The vagus nerve, the longest of the cranial nerves, controls your inner nerve center—the parasympathetic nervous system. And it oversees a vast range of crucial functions, communicating motor and sensory impulses to every organ in your body. New research has revealed that it may also be the missing link to treating chronic inflammation, and the beginning of an exciting new field of treatment for serious, incurable diseases. Here are nine facts about this powerful nerve bundle.

1. THE VAGUS NERVE PREVENTS INFLAMMATION.

A certain amount of inflammation after injury or illness is normal. But an overabundance is linked to many diseases and conditions, from sepsis to the autoimmune condition rheumatoid arthritis. The vagus nerve operates a vast network of fibers stationed like spies around all your organs. When it gets a signal for incipient inflammation—the presence of cytokines or a substance called tumor necrosis factor (TNF)—it alerts the brain and draws out anti-inflammatory neurotransmitters that regulate the body’s immune response.

2. IT HELPS YOU MAKE MEMORIES.

A University of Virginia study in rats showed that stimulating their vagus nerves strengthened their memory. The action released the neurotransmitter norepinephrine into the amygdala, which consolidated memories. Related studies were done in humans, suggesting promising treatments for conditions like Alzheimer’s disease.

3. IT HELPS YOU BREATHE.

The neurotransmitter acetylcholine, elicited by the vagus nerve, tells your lungs to breathe. It’s one of the reasons that Botox—often used cosmetically—can be potentially dangerous, because it interrupts your acetylcholine production. You can, however, also stimulate your vagus nerve by doing abdominal breathing or holding your breath for four to eight counts.

4. IT'S INTIMATELY INVOLVED WITH YOUR HEART.

The vagus nerve is responsible for controlling the heart rate via electrical impulses to specialized muscle tissue—the heart’s natural pacemaker—in the right atrium, where acetylcholine release slows the pulse. By measuring the time between your individual heart beats, and then plotting this on a chart over time, doctors can determine your heart rate variability, or HRV. This data can offer clues about the resilience of your heart and vagus nerve.

5. IT INITIATES YOUR BODY'S RELAXATION RESPONSE.

When your ever-vigilant sympathetic nervous system revs up the fight or flight responses—pouring the stress hormone cortisol and adrenaline into your body—the vagus nerve tells your body to chill out by releasing acetylcholine. The vagus nerve’s tendrils extend to many organs, acting like fiber-optic cables that send instructions to release enzymes and proteins like prolactin, vasopressin, and oxytocin, which calm you down. People with a stronger vagus response may be more likely to recover more quickly after stress, injury, or illness.

6. IT TRANSLATES BETWEEN YOUR GUT AND YOUR BRAIN.

7. OVERSTIMULATION OF THE VAGUS NERVE IS THE MOST COMMON CAUSE OF FAINTING.

If you tremble or get queasy at the sight of blood or while getting a flu shot, you’re not weak. You’re experiencing “vagal syncope.” Your body, responding to stress, overstimulates the vagus nerve, causing your blood pressure and heart rate to drop. During extreme syncope, blood flow is restricted to your brain, and you lose consciousness. But most of the time you just have to sit or lie down for the symptoms to subside.

8. ELECTRICAL STIMULATION OF THE VAGUS NERVE REDUCES INFLAMMATION AND MAY INHIBIT IT ALTOGETHER.

Neurosurgeon Kevin Tracey was the first to show that stimulating the vagus nerve can significantly reduce inflammation. Results on rats were so successful, he reproduced the experiment in humans with stunning results. The creation of implants to stimulate the vagus nerve via electronic implants showed a drastic reduction, and even remission, in rheumatoid arthritis—which has no known cure and is often treated with the toxic drugs—hemorrhagic shock, and other equally serious inflammatory syndromes.

9. VAGUS NERVE STIMULATION HAS CREATED A NEW FIELD OF MEDICINE.

Spurred on by the success of vagal nerve stimulation to treat inflammation and epilepsy, a burgeoning field of medical study, known as bioelectronics, may be the future of medicine. Using implants that deliver electric impulses to various body parts, scientists and doctors hope to treat illness with fewer medications and fewer side effects.

13 Facts About Ovaries

Ovaries are only about the size of large grapes, but they’re one of the most important organs in the female body. Their primary responsibilities include producing eggs and secreting sex hormones that promote fertility. In this way, the future of humanity depends on them. Read on to learn more about these tiny but mighty organs.

1. THEY’RE THE FEMALE GONADS.

Go ahead and laugh, but gonads was a scientific term long before it became slang for a man’s testicles. It actually refers to the reproductive glands of both sexes: ovaries for women, and testes for men. When an embryo is in the early stages of development (around the seventh week), its gonads have the potential to develop into either female or male sex organs through a process called sexual differentiation. By this point, the sex has already been pre-determined by chromosomes (XX or XY), and in the absence of a Y chromosome, the gonads turn into ovaries. One study of adult mice found that ovaries could be turned into testes by deleting a single gene called FOXL2, which is constantly working to suppress the development of male anatomy in mammals. However, it's unknown what effect the modification of this gene would have on humans.

2. THEY’RE CONTROLLED BY THE BRAIN.

The hypothalamus and pituitary gland both play pivotal roles in ensuring the ovaries function as they should. Neither is located anywhere near the ovaries, though. “If you put your finger between your eyes and shoved it backwards into your brain, first you would knock into your pituitary gland, which is a little pea-sized gland,” Randi Epstein, a New York City-based medical doctor and writer, tells Mental Floss. “And if you kept ramming backwards, then you would hit the hypothalamus.” (Of course, she doesn’t recommend actually trying this.)

The hypothalamus is the hormone control center, while the pituitary gland is called the body’s "master gland" because it controls the thyroid and adrenal glands, as well as the ovaries and testicles. Essentially, the hypothalamus tells the pituitary gland to send hormones to the ovaries, and the ovaries respond by secreting their own batch of hormones. A signal is then sent back to the hypothalamus to let it know if the levels of estrogen and progesterone are too high or too low. The cycle then continues, but we don't fully understand what triggers the hypothalamus and kicks off the process in the first place, Epstein says.

3. IT’S HARD TO ACCURATELY PREDICT WHEN OVARIES WILL KICK OFF MENOPAUSE.

Because of the previously mentioned unknowns, there’s no way of telling when puberty or menopause will occur. In the latter case, scientists have been looking at different genetic markers in an attempt to predict when the ovaries will shut down the processes of menstruation and ovulation—otherwise known as menopause—but "nothing is definitive" right now, according to Mary Jane Minkin, an obstetrician-gynecologist in New Haven, Connecticut, who also teaches at the Yale School of Medicine.

However, family history and age offer some clues. The average age for menopause in the U.S. is 51, but if all the women in your family went through menopause in their forties, there’s a good chance you will, too. Women who have had hysterectomies may also go through menopause one or two years earlier than they normally would, even if they have otherwise healthy ovaries. That's because the surgery is believed to reduce the flow of blood to the ovaries, resulting in a lower supply of hormones and therefore earlier ovarian failure.

4. SMOKING CAN ALSO TRIGGER EARLIER MENOPAUSE.

The effects of smoking on internal organs aren’t pretty, and the ovaries are no exception. “Smoking rots ovaries,” Minkin tells Mental Floss. “Basically, if you want to go through menopause earlier, smoke cigarettes.” Doing so can accelerate the onset of menopause by one to two years, and studies have shown that smoking hurts overall ovarian function as well.

5. THEY CHANGE SHAPE OVER TIME.

Ovaries get bigger and morph into the shape of an almond when girls reach adolescence, eventually reaching roughly 1.4 inches in length. Later in life, once menopause has occurred and the ovaries have fulfilled their purpose, they dwindle to under an inch long. “They just sort of poop out and they shrink, so the size gets exponentially smaller,” Minkin says.

6. WHEN A GIRL IS BORN, HER OVARIES HOLD ALL THE EGGS SHE’LL EVER HAVE ...

Female fetuses can carry as many as 7 million oocytes (immature eggs) in their ovarian follicles, and by the time they’re born, that number drops to about 2 million. Here's a mind-boggling fact: If a woman is pregnant with a girl, that means she’s also carrying her potential grandchildren, too.

Many of these eggs die off before a girl reaches reproductive age, though. By the time she starts going through puberty, she has about 300,000 left. About 1000 or so eggs are lost each month after that. When it’s all said and done, only about 400 mature eggs go through ovulation, at which point they’re dropped from the ovaries, through the fallopian tubes, and into the uterus.

7. ... BUT STEM CELL RESEARCH COULD CHANGE THAT.

Research in recent years has suggested that ovarian stem cells could someday be used to grow new egg cells, or to delay or stop menopause in women. Both of these tasks have already been successfully carried out in mice. "If we could gain control of the [human] female biological clock ... you could arguably delay the time of ovary failure, the primary force behind menopause,” researcher Jonathan Tilly told National Geographic in 2012.

For now, women faced with a diminishing supply can have their unfertilized eggs frozen through the process of cryopreservation. It’s meant to improve a woman’s chances of conceiving at a later date, but it isn’t guaranteed to work. “It’s getting better, but it’s hardly perfect,” Minkin says. “You can freeze the eggs, but you don’t know how viable they’re going to be in the long-term.”

8. SCIENTISTS HAVE CREATED 3D-PRINTED OVARIES FOR MICE.

In 2017, scientists used “porous scaffolds from a gelatin ink” to 3D-print synthetic ovaries for mice, The Guardian reported. Those ovaries were then filled with follicles containing immature egg cells, which allowed the mice to give birth to healthy babies. Scientists hope this technique will someday be used to restore fertility to women whose ovaries have been damaged by cancer treatments.

9. OVARIES CHILL OUT ON BIRTH CONTROL PILLS.

Oral contraceptives prevent ovulation by providing all the estrogen and progesterone that the body needs. With the ovaries’ job taken care of, they get to go on “vacation,” Minkin says. When contraceptive pills are used for five or more years, they reduce a woman’s risk of ovarian cancer by 50 percent. That’s because “funky things can happen” during ovulation, at which time the ovaries are at greater risk of an aberration, Minkin says. On the other hand, if the ovaries aren’t releasing eggs, there’s less of an opportunity for mistakes to happen. The ovaries are also less exposed to naturally occurring hormones that may promote the growth of cancer.

10. SOME CHRONIC CONDITIONS AFFECT THE OVARIES.

One of the most common problems affecting the ovaries are cysts. These fluid-filled sacs can form when an egg isn’t properly released from an ovarian follicle, or if the empty follicle sac doesn’t shrink after it bursts open to release an egg. Fortunately, these cysts often go away on their own. They only become a problem if they grow, or multiple cysts form. Strange things can happen, though. In one recent case, surgeons found a cyst containing a miniature skull and brain tissue inside the ovary of a 16-year-old girl. Yes, you read that right. It's called a teratoma —from the Greek word for monster—and it happens when the reproductive cells go rogue and start developing their own way.

Another disorder that can sometimes affect the ovaries is endometriosis. This occurs when tissue that’s similar to the endometrium, which lines the uterus, starts growing somewhere outside the uterus and causes a chronic inflammatory reaction. It can attach to the bladder, bowel, ovaries, or other areas. Symptoms may be minimal, severe, or somewhere in between, and the tissue can be removed through a minor surgery if needed.

Polycystic ovary syndrome (PCOS) is another fairly common problem, and it’s caused by a hormonal imbalance that in turn creates problems for the ovaries. Ovulation may not go as smoothly, periods can be irregular, and cysts can develop. Since there’s no cure, it’s a lifelong condition, but the symptoms can be managed.

11. CUNNING SALESMEN ONCE SOLD ANTI-AGING OVARY TONICS.

Miracle elixirs made from animal ovaries and testes were a big “money-making fad” in the early 20th century, Epstein writes in her book Aroused: The History of Hormones and How They Control Just About Everything. According to the sales pitch at the time, sex organs give life, so it’s only logical that they would help boost your energy and libido. “We were taking rabbit ovaries, crushing them up, desiccating them, and using them as a fertility or anti-aging treatment,” Epstein tells Mental Floss. One of the first “cures” for menopause and menstruation symptoms wasn’t much better, either. The main active ingredient was alcohol.

12. BIRDS HAVE JUST ONE FUNCTIONAL OVARY.

Unlike their dinosaur ancestors, birds have only their left ovary. Scientists theorize that birds lost an ovary over the course of evolution because it helped reduce their weight, making it easier for them to fly. This explains why dinosaurs laid loads of eggs, but birds lay just a few at a time.

13. SOME ANIMALS CAN SWITCH SEXES BY CHANGING THEIR OVARIES.

All clownfish are born male, but they’re able to change sex at will. This is because they have both mature testes and immature ovaries, the latter of which can develop if the alpha female in a school of fish dies. (As Business Insiderpoints out, a scientifically accurate Finding Nemo would have been significantly more disturbing.)

Parrotfish can change sex as well—mostly from female to male. During this transition, the ovaries dissolve and testes are grown. “In general, for species where big males can control access to females (think harem), it pays to be female when small (you get to reproduce with the dominant male) and then turn into a male when you are big enough to duke it out with a competing male to win access to a group of females,” writes Marah Hardt, author of Sex in the Sea.